Air filters are commonly used for particulate material filtration and gaseous chemical decontamination for residential, commercial, industrial and any other applications requiring air treatments, including but not limited to air cleaning, air purification, air deodorizing, air decontaminating.
The U.S. Pat. No. 5,779,747 discloses a flexible folded filter insert which is not noticeably deformed by the air which it cleans. The insert has a fold pattern which is closed off at the end by flexible strips which can be compressed in the longitudinal direction. Because of the elasticity of the strips, torsion of the folded filter insert relative to an axis along the fold pattern and/or bending with reference to at least one axis crosswise to the fold pattern is possible.